Particular Signal Cancel Method, Particular Signal Cancel Device, Adaptive Filter Coefficient Update Method, Adaptive Filter Coefficient Update Device, and Computer Program

1. An adaptive filter coefficient update method of receiving a mixture containing a target signal, a particular signal that should be canceled, a stationary noise, and a non-stationary noise, subtracting an adaptive filter output from the above mixture, and obtaining an error signal, comprising: (a) a process of estimating a stationary noise, by a stationary noise estimation unit, from said error signal and obtaining a stationary noise estimated value; (b) a process of estimating a non-stationary noise, by a non-stationary noise estimation unit, from said error signal and obtaining a non-stationary noise estimated value; (c) a process of mixing said stationary noise estimated value and said non-stationary noise estimated value, by a mixing unit, and obtaining a mixed noise estimated value; (d) a process of calculating a coefficient update step size, by a step size calculation unit, such that the coefficient update step size takes a value between 0 and 1 based on said mixed noise estimated value; and (e) a process of updating a coefficient of the adaptive filter, by an update amount calculation unit, by employing the above step size.

2. The adaptive filter coefficient update method according to claim 1 , wherein said process (a) obtains a new stationary noise estimated value when a power of said reference input signal is smaller than a predetermined value, and said error signal is smaller than said stationary noise estimated value multiplied by a constant.

3. The adaptive filter coefficient update method according to claim 1 , wherein said process (a) obtains said stationary noise estimated value when said reference input signal power is smaller than the predetermined value, and said error signal is larger than a constant times said stationary noise estimated value, or when said reference input signal power is larger than the predetermined value, and said error signal is larger than a constant times said stationary noise estimated value.

4. The adaptive filter coefficient update method according to claim 1 , wherein said process (c) controls a ratio of said stationary noise estimated value and said non-stationary noise estimated value being included in said mixed noise estimated value so that the stationary noise estimated value is included more than the non-stationary noise estimated value when a difference between a power of said error signal and said stationary noise estimated value is smaller than a predetermined value close to 0.

5. The adaptive filter coefficient update method according to claim 4 , wherein said process (c) controls said ratio based upon a coefficient vector of said adaptive filter.

6. An adaptive filter coefficient update device that receives a mixture containing a target signal, a particular signal that should be canceled, a stationary noise, and a non-stationary noise, subtracts an adaptive filter output from the above mixture, and obtains an error signal, said adaptive filter coefficient update device comprising: a stationary noise estimation unit that estimates a stationary noise from said error signal and obtains a stationary noise estimated value; a non-stationary noise estimation unit that estimates a non-stationary noise from said error signal and obtains a non-stationary noise estimated value; a mixing unit that mixes said stationary noise estimated value and said non-stationary noise estimated value, and obtains a mixed noise estimated value; a step size calculation unit that calculates a coefficient update step size such that the coefficient update step size takes a value between 0 and 1 based on said mixed noise estimated value; and an update amount calculation unit that calculates an update amount for updating a coefficient of the adaptive filter by employing the above step size.